US 7332052 B2
An energy efficient method and apparatus for manufacturing a biodegradable, compostable, liquid-impermeable lined paper bag for containing wet (i.e. food) wastes by which all adhesives used in the process are cold glues applied without using heat and are applied through an extrusion and/or metering application means. Cellulose film is advantageously used for the paper liner and a dot matrix configuration of adhesive is applied between the cellulose and paper layers to laminate them together. The matrix-defined size of spacings between the points of application of adhesive on the cellulose film is such that both loss of the permeability of the cellulose film to water vapour and oxygen and creation of stress points on the cellulose film are minimized. A second cold glue is applied to the bag bottom section by a matrix of extrusion adhesive guns and programmable controller for activating the guns whereby the guns are activated according to a program of the controller for applying the second adhesive to pre-determined, programmable areas of the bag bottom section.
1. A method of making a wet waste compostable bag comprising cellulose-laminated paper, said method comprising the steps:
(a) providing a cellulose film and paper sheet for lamination together to form said cellulose-laminated paper;
(b) applying to a surface of one of said cellulose film and paper sheet a biodegradable adhesive having a dot matrix configuration wherein said dot matrix configuration of adhesive covers all of said surface of said film or sheet to be laminated together and spacings between dots of said dot matrix configuration are preselected to permit passage of water vapour and oxygen through said cellulose-laminated paper and reduce any creation of stress on said cellulose of said cellulose-laminated paper;
(c) overlaying said cellulose film and paper sheet whereby said biodegradable adhesive is between said cellulose film and paper sheet and applying sufficient pressure to said overlaid film and paper sheet to form a web of said cellulose-laminated paper; and,
(d) forming said laminate web to produce said wet waste compostable bag.
2. A method according to
(a) forming said web into a tube and cutting said tube to produce bag pieces;
(b) folding one end of each said bag piece to configure a bag bottom section with flaps;
(c) applying a second biodegradable adhesive to said bag bottom section; and,
(d) folding said flaps over said bag bottom section and applying sufficient pressure thereto for said second biodegradable adhesive to affix said flaps in said folded position and provide a closed bag bottom.
3. A method of making a wet waste compostable bag according to
4. A method of making a wet waste compostable bag according to
5. A method of making a wet waste compostable bag according to
6. A method of making a wet waste compostable bag according to
7. A method of making a wet waste compostable bag according to
This application is a divisional of U.S. patent application Ser. No. 10/313,105, filed on Dec. 6, 2002 and issued as U.S. Pat. No. 7,128,704 on Oct. 31, 2006, now which is a divisional of U.S. patent application Ser. No. 09/572,130, filed May 17, 2000, now U.S. Pat. No. 6,524,667, issued on Feb. 25, 2003, both of which are herein incorporated by reference in their entirety.
This invention relates to an energy efficient method and apparatus for manufacturing of a biodegradable, compostable, liquid-impermeable lined paper bag for containing wet (i.e. food) wastes by which all adhesives used in the process are cold glues applied without using heat and are applied through an extrusion and/or metering application means.
For environmental reasons government authorities are increasingly either encouraging or requiring household occupants to recycle their waste products. In the past this was typically limited to dry waste such as leaves and lawn clippings, glass, paper and tin but, more recently, compostable wet waste materials such as food and table scraps are also being considered recyclable (through the use of cellulose-lined paper compostable bags).
According to some of the known and used manufacturing methods for wet waste bags an inner polymer layer is laminated to an outer paper layer(s) using heat to activate glues such as starches and/or to melt and seal the film coatings. However, such methods are disadvantageously expensive because they require much heat energy, involve multiple-step processing (in order to provide heating and drying periods for the glues) and require the purchase of relatively expensive hot application glues. Moreover, even if such polymer layers are comprised of biodegradable materials they typically do not degrade into compost as efficiently as does a cellulose film and, more disadvantageously, they are not permeable to allow the transfer of water vapour and oxygen there through which means that any bags lined with these materials cannot satisfactorily store wet waste such as food waste over any significant period of time because such wastes will undergo an anaerobic decomposition when the bag is sealed and exude foul odours.
Cellulose films provide substantial advantage over polymer films in that they are permeable to water vapour and oxygen yet are generally impermeable to liquid (note that although there exist cellulose films which are also permeable to liquid these types of films are not contemplated herein and all references herein to cellulose film refer to those films which are generally impermeable to liquid). However, they have associated with them two disadvantages, one being that they are relatively bristle and tend to break when stressed and the other being that they are degraded and damaged by heat. Consequently, a lamination of cellulose film to paper using the usual heat processes to heat the plasticized surfaces of the cellulose and affix it to the paper would cause damage to the cellulose and the resulting bag product would have a limited shelf life and low handling tolerance (since the cellulose layer would be prone to an early breaking and tearing away from the paper layer). Since the purpose of the bag is to effectively contain wet waste over a period of time, and the cellulose layer is used to retard the transfer of liquid (moisture) from the inside to the outside of the bag, such damage to the cellulose layer renders the product ineffective and unsuited to its purpose.
To minimize such heat exposure, reduce adhesive material usage and avoid blockage of the permeable membrane provided by the cellulose, it is known to apply glues to the cellulose in patches or strips. For example, U.S. Pat. No. 5,178,469 which issued to Woods End Research Laboratory on 12 Jan. 1993 discloses a biodegradable bag having a cellulose lining which is affixed to the paper layer using an adhesive which is applied, using drip feeders, in spaced strips between the paper and cellulose layers. However, such an uneven coverage of adhesive between the paper/cellulose layers produces relatively large spacings between the points of attachment of the cellulose and produces stress points at each new strip (patch boundary). In such products, where the cellulose joins to the paper there is an increased tendency of the cellulose to tear at these stress points. Also, such drip feeder means of applying glue is inherently inaccurate and disadvantageously wastes a significant amount of glue material.
A further disadvantage with the prior methods and means of making compostable bags is the excessive and/or ineffective usage of adhesives in the formation of the bag bottom. According to known processes the bag bottom is formed using adhesive applied by fixed roller applicators with a drip feed and this does not allow any control over the application either with respect to location or deposition volume. Since it is important that the bag bottom be fully closed off (i.e. sealed) to avoid leakage of liquid it is important that the score lines of the bag bottom and other fold areas of the bag bottom be effectively glued. Also, since biodegradable adhesives are relatively costly it is important that wastage of the glue be avoided and imprecise glue application means are inherently wasteful and non-economic.
Therefore, it is desirable to provide a cost effective means of making a wet waste compostable bag which allows for use of a cellulose layer without the application of heat thereto yet securely and fully adheres the cellulose to the paper layer without producing substantial stress points and with minimal interference of the permeability of the cellulose to water vapour and oxygen. Further, it is desirable to provide a means of more precisely and efficiently applying adhesive to those areas of the bag, particularly the bag bottom, which require placement of adhesive at specific locations for an effective formation of a wet waste bag.
In accordance with one aspect of the invention there is provided a compostable bag for containing wet waste and comprising cellulose-laminated paper, the cellulose-laminated paper comprising one or more adjacent outer paper layers and an inner cellulose film layer laminated to an innermost one of the paper layers by means of an adhesive in a dot matrix configuration. The matrix-defined size of spacings between the points of application of adhesive on the cellulose film is such that both loss of the permeability of the cellulose film to water vapour and oxygen and creation of stress points on the cellulose film are minimized. The adhesive is a cold glue and the cellulose film itself has a high water vapour transfer rate. Preferably the water vapour transfer rate through the bag is about 65% of the water vapour transfer rate of the cellulose film itself. The bottom of the bag comprises folds and layers of the cellulose-laminated paper wherein the layers are adhered together by means of a second adhesive which is preferably applied in a pre-determined, programmable pattern by a matrix of extrusion adhesive guns activated according to a program of a pre-programmed controller.
In accordance with another aspect of the invention there is provided a method of making a wet waste compostable bag. A first adhesive, being a cold glue, is applied to one of a cellulose film and paper sheet in a pre-determined dot matrix configuration. The matrix-defined size of spacings between the points of application of the first adhesive on the cellulose film is such that both loss of the permeability of the cellulose film to water vapour and oxygen and creation of stress points on the cellulose film of the resulting bag are minimized. The cellulose film and paper sheet are overlaid with the dot matrix configuration of adhesive between them and sufficient pressure is applied to the overlaid film and sheet to produce a cellulose film/paper laminate web and the laminate web is formed into a tube. The tube is cut into separate bag pieces and one end of each bag pieces is folded for configuring a bag bottom section with flaps. A second adhesive is applied to the bag bottom section and the flaps are folded together over the bag bottom section. Sufficient pressure is applied for the adhesive to affix the folded flaps and provide a closed bag bottom. The second adhesive, being a cold glue, is preferably applied to pre-determined, programmable areas of the bag bottom section by means of a matrix of extrusion adhesive guns activated according to a program of a pre-programmed controller.
In accordance with a further aspect of the invention there is provided apparatus for making a wet waste compostable bag comprising a matrix of extrusion adhesive guns and programmable controller for activating the guns whereby the guns are activated according to a program of the controller for applying adhesive to pre-determined, programmable areas of a bag bottom section. Preferably, the apparatus includes a rotatable frame supporting the matrix of adhesive extrusion guns whereby the frame is rotatable to production and maintenance positions. The frame may be further rotatable to a bag jam position and means may be provided for automatically causing the frame to move from the production position to the bag jam position on the occurrence of a paper jam in the area of the rotatable frame.
The present invention is described in detail below with reference to the following drawings in which like reference numerals refer throughout to like elements:
The two paper layers 110, 115 are adhered together by applying simple adhesive tacks in a web-end component 60 and a slitter (not shown) of component 60 slits the end of the web laminate to assist in the forming of the folds on the bottom of the bag. An adhesive extrusion plate 65 at the front end of component 60 precisely applies two thin spaced lines of adhesive to the inner paper layer along one side length of the paper web to provide for the bag seam when the web is turned to form a tube during the following step. At the time the cellulose and paper layers 105, 110 are overlaid (i.e. prior to their lamination) they are positioned in overlapping relationship so that the seam adhesive is applied to the paper only and not to the cellulose film. A web former 70 folds over approximately half the width of the paper/cellulose laminate web 120 to form the tube of the bag and at the same time a roller (not shown) applies pressure to the underside of the seam adhesive area so as to complete the tube formation. A servo drive motor 75 provides the rotation which draws the three-layer tube into the forming area of an H.G. Webber 9 AW SOS bag machine 80. In the bag machine 80 the tube is cut to the required length for the bag using a rotating cutoff knife (not shown) and a series of grippers and folders (not shown) form the bottom sections of the bag such that a double inside bottom fold (i.e. without any gap), as shown by reference 18 in
For the paper layers 110 and 115 a virgin, wet strength Kraft paper provided by Tolko Paper of Le Pas, Manitoba, Canada under the designation SPK (Speciality Produced Kraft) is preferred for use. A recycled kraft paper product could instead be used if it is chosen to do so but such papers typically comprise substantially higher trace elements of metals and these trace elements would be found in the composted bag materials of bags made with such recycled paper. For the cellulose film the applicant uses a specially formulated film product produced by UCB S.A. of Belgium under the product code 320 DM and, unlike prior cellulose films, this film, being fully compostable, does not comprise phalates (which are undesirable for submission into the food chain). This cellulose film is a transparent, one-side nitrocellulose coated film and is impermeable to liquid. Unlike the prior cellulose films which include a plasticizer on each side (plasticizer being necessary to hold together the cellulose material in the form of a film and also to provide the required impermeability to liquids) and for which heat lamination processes are used to melt the plasticizer, the cellulose film 105 used for this preferred embodiment has only one side coated with a plasticizer and the other surface thereby permits successful lamination without the use of heat and using only a cold glue process within the laminator 50. Advantageously, this one-sided cellulose film 105 also has a very high water vapour transfer rate of 6.4 grams per 100 square inch area over a 24 hour period and a good oxygen transfer rate of 0.52 grams per 100 square inch area over a 24 hour period. Good water vapour and oxygen transfer is necessary in order to maintain an aerobic status of the food waste while the bag is sealed. Without such a transfer, through the paper/cellulose film laminate 120, an anaerobic decomposition of the food waste will occur and this would result in the creation of unsatisfactory odours.
The laminator 50 shown in
As shown in
For the preferred metering cover 135 used by the applicant the crown diameter D of the projections is 0.032 inch, the height H of the projections is 0.045 inch, the pitch P of the projections is 0.030 inch and the thickness T of the cover 135 is 0.105 inch. For this particular dot matrix projection spacing and size the resulting bag 55 achieves about 65% of the water vapour transfer rate (WVTR) of the cellulose film 105 itself (which has the high value of 6.4 g/100 sq.in./24 hrs) and this means that the WVTR value of the bag is also very high as compared with prior known wet waste compostable bags. The oxygen transfer rate is about the same for the resulting bag 55 as for the cellulose film 105 itself. The dot projections 175 are equally spaced and have preselected diameters and surface areas at the crown, whereby these parameters may be varied to control (i.e. meter) the amount of glue which is applied to the cellulose film 105 and, in turn, the permeability (WVTR) of the paper/cellulose laminate and the resulting bag 55. The height H of the dot projections 175 can also affect the results of the lamination process because too small a height can result in a build up of glue between the crowns of the projections and an excess of glue being applied to the cellulose film causing a full-surface coverage of the film and poor permeability performance. Therefore, by appropriately pre-determining these parameters of the projections the lamination process and the performance of the resulting bag can be controlled according to the desires of the manufacturer.
Advantageously, the combination of the three layers of the web laminate, being the paper layer, the glue layer and the cellulose layer, produces an increased tensile strength of the resulting bag.
Following the tube processing 70 of the paper/cellulose film laminate web (see
The bottom extrusion numerical system (BENS) of the invention, and its positioning relative to the rotating drum 90, is shown in
As shown in
The gluing system comprising the guns 370, glue lines 365 and manifolds 350 is completely enclosed and until the glue is actually extruded from the guns for deposit onto the bottom bag 5 it is not exposed to air. The firing of the glue guns 370 is controlled by a programmable PC55 Series control unit (not illustrated herein) which is also produced by Nordson Corporation of the U.S. and was appropriately modified by the applicant for the 16 gun, 4 manifold system of the illustrated embodiment. Information concerning the PC55 may be found at the Website of Nordson Corporation at the Internet site address www.nordson.com/packaging/pc50.htm which is incorporated herein by reference. In the selected configuration the glue guns are grouped into four separate control zones such that four separately controllable areas are provided. The manifold 350 labelled A in
The BENS apparatus further includes Nordson Corporation glue pumps (two being used with two double action piston pumps) and an air valve system with a servo proportional valve (by which the glue volume deposited is maintained regardless of any change in speed of the drum 90). The operating speed of the bag machine is approximately 110 bags per minute.
The activation of the glue gun control unit is triggered by the arrival of the bag 27 at the target position T when photo sensors (not shown) sense the flap corners 200 (see
For purposes of programming the glue control unit the servo motor 75 produces 3600 pulses during one rotation of the drum 90 and, thus, each pulse represents a perimeter increment equal to the drum perimeter divided by the total number of pulses (3600). In the preferred embodiment a 9AW size drum 90 is used so each increment is less than a tenth of an inch. The drum 90 provides four stations for the bag, each defining a quadrant of the drum, as shown by the numbers 14 on the drum of
The glue guns etc. of the BENS apparatus are protected from damage by a paper jam by the automatic release mechanism of the ball detent assembly 500 and limit switch 330 which are illustrated in
It is to be understood that the specific types and configurations of the machine components described herein with reference to the illustrated preferred embodiment are not intended to limit the invention; for example, the invention is not intended to be limited to any specific configuration for the adhesive metering plate of the laminator or extrusion guns of the BENS apparatus, for which various alternative embodiments may be determined by one skilled in the art based upon the teachings herein and the particular application. Further, it is to be recognized that the BENS apparatus disclosed and taught herein is not limited to use on any particular type of bag composition or laminate such as the cellulose-lined type of bag material used for the preferred embodiment disclosed herein (possible alternative materials being a biodegradable polymer-lined type bag material or other liquid impermeable film-lined type bag material). Rather the invention is defined by the appended claims.
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